Also known as RL18_ACTP2, rplR. This is one of the proteins that binds and probably mediates the attachment of the 5S RNA into the large ribosomal subunit, where it forms part of the central protuberance. Part of the 50S ribosomal subunit; part of the 5S rRNA/L5/L18/L25 subcomplex. Contacts the 5S and 23S rRNAs.